Diomca Muscipula, l-.llis. 33 



the passage through the pore aperture ( Plate IV, Figs. 9, 9*7). 

 The transverse or oblique walls are traversed by five to 

 eight similar processes, so that the protoplasm of each epider- 

 mal cell is linked to that of neighbor cells by fifty to seventy- 

 five fine connecting threads, and these again collectively 

 are united with the cylinder of sensitive cells in the irri- 

 table hairs. 



But the lower or internal wall surfaces of the epidermal 

 cells have a clear shining white aspect due to colloid modifi- 

 cation (Plate IV, Figs. 6, 7). After the most careful treat- 

 ment and study, we have failed to trace a single process 

 traversing these. On the other hand, where the lowest pair of 

 cells of each gland unites with the sub-epidermal cells their 

 walls are thin and traversed by protoplasmic threads. Gar- 

 diner has already mentioned l the occurrence of connecting 

 threads in the mesophyll, and we have succeeded in tracing 

 these throughout most of the cells ; the threads are less 

 abundant, however, than are those of the epidermal cells. 



Taken as a whole, then, the irritable hair cells communicate 

 by their epidermal and mesophyll portions with the leaf epi- 

 dermis and mesophyll generally, while the mesophyll cells of 

 the leaf substance appear to be cut off from the epidermis 

 by a thickened wall, but communicate directly with the gland 

 cells. The advantage of this is probably considerable even 

 from a mechanical standpoint, if we remember the amount of 

 tension to which the surface cells are exposed under the vary- 

 ing conditions of expansion and contraction of the leaf, as 

 well as the secretion of the digestive liquid. 



Several of the observers already mentioned have described 

 the structure of transverse sections, but they have overlooked 

 points that appear to be of considerable importance. When 

 the leaf is open and undisturbed, the upper and under epider- 

 mal and subjacent three cell-layers of the mesophyll contain 

 chloroplasts and large starch granules. But further, little 

 patches of chlorophyll cells unite these with the bundles or 

 are irregularly disposed in patches amongst the clear meso- 

 phyll cells, and all of them contain starch. The bast cells of 



« Proc. Roy. Soc, Vol XXXVI, p. 181. 

 3 



